Question

Weekly commodity prices for heating oil (in cents) were obtained for a period of 30 consecutive weeks and regressed against time (using time values of 1, 2, … 30). Based on the regression output shown below, and using a level of significance of 0.05: The regression equation is Price (cents) = 128.112 + 1.078 Time

Predictor	Coefficent	SE Coefficent	T	Pvalue
Constant	128.112	2.092	61.25	0.000
Time	1.0782	0.1407	7.66	0.000

S= 5.07299 R-Sq= 71.9%

Durbin-Watson statistic= 0.2448

i) Is there a positive or negative autocorrelation among the residuals? Test using α = 0.05.

ii) Find the adjusted r² for the model.

iii) What is the predicted price at time 20?

Answer 1